Past efforts to design improved, practical autoloading shotguns generally have been constrained by the effects of firing recoil, or by inadequately considering the effects of recoil when designing the gun. (The term "autoloading" is here used to denote a gun which, when fired, automatically ejects the spent shell and loads a fresh round from a magazine, and includes semi-automatic as well as full-automatic firing modes.) Although recoil affects any firearm to some degree, the relatively heavy recoil of shotguns is recognized by most shooters. Particularly in larger-gauge shotguns, recoil causes discomfort to the shooter and, in the case of autoloading shotguns, prevents effectively tracking a target with repeated fire, that is, for more than one round.
The undesirable effects of recoil are particularly troublesome when designing and using shotguns intended for full-automatic fire, or so-called assault shotguns. Law enforcement agencies and military applications have desired the close-range firepower and intimidating effects of a shotgun capable of selective full-auto firing, but the repeated recoil of, say, a 12-gauge shotgun firing full-auto makes such guns very difficult for most shooters to control.
The effects of recoil have caused other problems in past efforts to design shotguns capable of full-automatic firing. Such firearms require a substantial cartridge capacity in order to be effective, and increased cartridge capacity is obtained with either a box magazine or drum magazine. Past efforts to design full-automatic shotguns using either box or drum magazines have generally been unreliable, due to the relatively high recoil of the conventional shotgun. As a shotgun equipped with a box or drum magazine kicks backwardly and rearwardly when fired, the inertia of shotgun shells in the magazine resists this movement. This inertia effect causes the shells to compress the magazine spring and move downwardly relative to the magazine feed lips which move rearwardly during firing, or put differently, the shells because of their inertia momentarily stay put in space while the shotgun and magazine suddenly move back and up due to recoil. This inertia effect takes place while the bolt assembly, having ejected the spent shell, is moving forward to chamber a fresh round from the magazine. The top round in the magazine may still be below the magazine feed lips due to the inertia effect of recoil, so that cartridge loading from the box or drum magazine is unreliable.
Past efforts to overcome the inertia effect on box and drum magazines have involved modifications to the magazine, but such modifications have generally been unsuccessful. Consequently, most autoloading shotguns (whether or not capable of full-auto firing), are equipped with tubular magazines. The limited cartridge capacity and relatively slow one-round-at-a-time reloading of tubular magazines makes these magazines an undesirable substitute for box or drum magazines, in autoloading shotguns designed or intended for law enforcement or combat applications.